Carbon materials composed of carbonaceous cured bodies are used as the electrode materials in, for example, lithium-ion secondary batteries, electrical double-layer capacitors, and capacitors.
For example, a carbon material is used as the negative-electrode active material in lithium-ion secondary batteries. A “rocking chair-type” battery configuration is employed in which lithium in an ionic state is intercalated into the carbon material during charging of the battery, and is deintercalated as ions during battery discharge.
As the trend toward smaller sizes and greater functionality in electronic devices proceeds apace, there exists a growing need for even higher energy density in lithium-ion secondary batteries. However, the graphite making up the carbon material is limited to the theoretical lithium intercalation/deintercalation capacity of 372 mAh/g. Hence, a negative-electrode material having a larger lithium intercalation/deintercalation capacity is desired.
To address this need, methods of using silicon materials in place of carbon materials that have a low charge/discharge capacity are being investigated. However, silicon materials experience large changes in volume from charging and discharging, as a result of which the electrode material sometimes incurs damage when continuous charging and discharging is carried out. This has led to investigations also on carbon-silicon composite materials (e.g., see Patent Documents 1 to 4). However, even with such carbon-silicon composite materials, the problem of damage to the material due to volumetric changes in the silicon present therein has yet to be fully resolved.